Locals told a group of academics who visited Bang Ka Cher fishing village near Mae Ramphung beach that their lives are still tainted by the slick.
Bang Ka Cher fishing community is just north of the area where the oil spill was washed ashore.
About 50,000 litres of crude oil leaked into the sea when a pipeline of PTT Global Chemical Plc (PTTGC) broke on July 27.
The spill polluted Ao Phrao beach on Koh Samet and later spread to the mainland in Rayong.
The villagers, who are mostly fisherfolk, said that fish and marine life appeared to have disappeared from the sea.
Weerasak Pongnarong, a Bang Ka Cher villager, said daily catches had dropped markedly.
Normally, local fishermen would be able to catch between 40kg and 50kg of fish on each trip. Now most were complaining their catch has dropped to only 2kg.
Many of the fishermen were thinking of giving up their fishing jobs and turning to construction work, he said.
A seafood restaurant operator identifying herself as Tassamol said her income has also fallen drastically because fewer people now visit Rayong since the environmental mishap.
She said she used to sell 5,000 baht of food a day but her daily income has now dropped to 200-800 baht.
Some restaurant owners had decided to close their businesses temporarily.
Chaturat Iam-woranirand, president of the local Small-Scale Fishery Association, said state agencies were placing the wrong emphasis in restoring the image of Rayong.
They were revving up tourism promotion campaigns when they should pay more attention to the sea environment, he said.
The villagers said they had doubts the provincial coastline was completely free from chemical pollution caused by the spill.
Piles of tar balls are washed ashore every day. Shells of young cuttlefish were also found on the beach, which academics said was an indication of chemical pollution in the water.
PTTGC said on its website it had paid 4,414 villagers 30,000 baht each to compensate them for the impact of the oil spill. Total compensation amounted to 170 million baht.
Many villagers said they still felt the amount was not sufficient to compensate for the damage they suffered and they were now discussing possible legal action against the firm. Ecological Alert and Recovery Thailand (Earth) director Penchome Sae-Tang said the compensation did not reflect the true extent of damage since chemical contamination in the sea, left by the clean-up operation, could remain for months.
The compensation should be based on the damage which each individual had suffered and this needed to be surveyed on a case-by-case basis.
PTT Oils Spill Watch, formed by Earth, the Environmental Law Foundation, Greenpeace Southeast Asia and Good Governance for Social Development and the Environment Institute petitioned the government on Aug 27 to reassess the environmental impact of the oil spill.
About 32,000 people have signed the petition. The government said it had passed the petition to the Energy Ministry for a decision.
Ms Penchome said the group would step up its campaign to pressure the government for an independent body to reinvestigate the spill. The move includes a survey this month to establish the true impact of the oil spill on the environment and the economy, and the extent of damage suffered by locals.
A probe committee set up by the energy minister found last month that PTTGC correctly handled the oil leak, but bad weather and a customs procedure holding up the arrival of an aircraft to fight the slick aggravated the spill's impact.
The firm acted appropriately in using dispersants and calling in a plane for spraying.
However, booms put in place to contain the spill did not work well due to strong winds and currents, the committee found.